Rheostat



Patented Aug. l2, 1924.

UNITED STATES PATENT OFFICE.

PAUL E. KLOPSTEG, E CHICAGO, ILLINOIS, ASSIGNOR T0 TRAL SCIENTIFIC COM- PANY, 0F CHICAGO, ILLINOIS, A. CORPORATION OF ILLINOIS.

-nnnosran application and nay 31,1922. serai: no, 564,768.

To all whom it may concern.' v

Be it known that I, PAUL E- Knors'rno, a citizen of the United States, residing at Chicago, in the county of Cook and State 6 of Illinois, have invented certain new and useful Improvements in Rheostats, of which the following is a specification. This invention relates to rheostats and has for its object broadly to improve the I0 construction and operation of sliding contact rheostats whereby their capacity and y turns is included 1n the clrcuit. Such an utility are increased.

A further object of the invention is to provide a rheostat in which heat generated l 1n the resistance will be rapidly removed.

A further object of the invention is toA provide a sliding contact rheostat having a. plurality of resistance units arran ed to permit the units or portions thereo to be connected either in parallel or in series.

A further object of the invention is to combine a rheostat with a Huid receptacle so that the resistance may be used as a heating unit for delivering a uniform supply of fluid at a constant temperature.

Further objects of the invention will become apparent as the description is read in connection with the accom anying drawing illustrating selected embodlments of the invention and in which Fig. 1 is a side-elevation of one form of sliding contact rheostat embodying my invention;

Fig. 2 is a diagram illustrating one use of the rheostat shown in Fig. 1; and

Fig. 3 is a diagram illustrating the arrangement of the various elements when two units of resistance are used.

I have illustrated the invention in Fig. 1 in a form resembling the conventional sliding contact rheostat used largely in laboratories and like places. The ordlnary construction includes a resistance coil wound on a suitable support or core 11 which is supported at its ends by metallic frames 12 t at carry at their upper ends a 'bar 14 on which a sliding contact similar to that shown at' 15 is mounted. The o posite ends of the coil 10 are electrical y connected with stra s 16 and 17 which are uipped with bin ing posts 18 and 19. T ere is also a bindin post 20 at one end of the bar 14' and anot er binding post may be provided at the other end of the bar.

In the conventional rheostat the core 11 is of slate or some similar non-conducting material and the wire forming the coil 10 isoxidized to form insulation between adjacent turns. In practice, when all of the resistance is to be used, connections are made to the binding posts 18 and 19; and when a part only of the resistance is required, connections are made to the binding posts 18 and 20, and the sliding contact 15 is moved along the coil until the required number of instrumentas this is limited in use to a comparatxvely small range of current, for 1n Y order to obtain a heavy current, in man cases it is necessary to include only a sma l number of turns of the resistance wire with the result that this small amount of wire becomes so highly heated as to break down the insulation or burn out the coil.

This can be partly overcome by mountin a second sliding contact on the bar 14 and making ,an electrical connection 22 between the binding posts 18 and 19. The sliding contact 21 may be a duplicate of the contact 15. The connection between the bindin posts here shown includes a section of meta tnbing23 clamped between the ears 24 of the stra 16 by the bolt 25 forming part of the binding post 18 and a similar section of tubing 26 connected in a like manner with the stra 17. The adjacent ends of the pieces o tubing 23 and 26 are joined by a rod of fiber or other insulating material 27 which is bridged by a knife switch 28. When a rheostat is equipped in this manner it can be connected as indicateddiagrammatically in Fig. 2 where 29 and 30 indicate the line, and L indicates a load. The current entering at 30 divides at the contact 15 a portion proceeding through the coil 10 from the point 3l to the binding post 19 and thence through the knife switch 28 to the binding post 18 where it joins the other portion of the current that has passed through the coil from the point 32 to the binding post 18. In this way the capacity of the rheostat is doubled. In other words, for the same heat generation, twice the currentcan be carried by the rheostat illustrated diagrammatically in Fig. 2 than can be transmitted by the conventional rheostat.

As the current increases in a short number of turns, the potential between adjacent turns increases, recpiiring additional or better insulation, for t is reason I prefer to use in the resistance coils enamel very similar to that found in magnets where the enamel is baked on, but is sullicently flexible to permit the necessary bending of the wire.

In order to further increase the capacity of the rheostat I preferably make the core in the form of a tube which may be of porcelain enameled steel, copper or the like and provided with an inlet 33 at the bottom of the left end and an outlet 34 at the top of the right end. The enameled metal or other insulating material of which the tube may be made will erform the functions of the slate or the like used in the conventional rheostat and at the same time will permit water or other Huid to circulate through the core to absorb the heat generated in the coil. It is particularly important that the outlet 34 be adiacent to the highest point in the core so that air` or other gases will not be trapped in the u per part of the tube theregy plreventing t e iiuid from taking away e eat. Preferably ,the inlet is located .at the bottom and the outlet at the top as shown.

An instrument of this kind can also be used to supply air, water or the like at substantially constant temperature by merely connecting 33 with a source of the desired 'fluid that will feed uniformly. For example; if water is desired at a certain temperature above normal, the-inlet 33 may be connected with the usual supply which is at substantially constant temperature and pressure, and the heat generated by passing the necessary current through all or part of the coil 10 will cause the water to be delivered from 34 at a proximately constant temperature. The

lated by adjusting the iiow of the fluid an the current.

In Fig. 3 I have shown diagrammatically a rheostat including Atwo units similar to that illustrated in Fig. 1 so arranged that they can be connected either in series or in parallel. The coils 35 and 36 may be wound on tubular cores like that shown in Fig. 1 or any other that may be found desirable. Two bars 37 and 38 are supported in a manner similar to that shown with reference to the bar 14 in Fig. 1. Each of these bars is provided with a slider 40 and 41'which may be physically connected as indicated in' Fig. 3 or physicallyl separated as may be desired. A. double t row switch 42 connected as shown will make it easy to use the resistance in parallel or in series. This switch has a terminal 43 connected with the left end of the coil 36, a terminal 44 connected with the left end of the coil 35, a terminal 45 connected with the header 39 and a terminal 46 connected with a terminal 47 which in turn is connected with one side 48 of the line.

esired transfer of heat can be The other side 49 of the lineV is connected through the load 50 with the left end of the coil 35. By throwing the switch so as to connect the terminal 46 with the terminal 45 and the terminal 43 with the terminal 44 the current will proceed from 48 through 47 and 45, through the header 39 to the bars 37 and 38, where a portion of the current will pass throu h the contact 41 to the coil 36 ,at 51, throu the coil to the terminal 43, through t e switch to 44, and through the wire 52 to 53 where it joins the remainder of the current that has passed throu h the contact 40 to the coil 35 at 54 and t rough the coil to 53.. From 53 the current passes through the load and the wire 55 to the other side of the line 49.

By throwing the switch so as to connect terminals l43 and 47 the current will proceed from 48 through 47 and the switch to 435 through the wire 56 to the coil 36, through the contacts 41 and 40 to the coil. 35 at 54 and thence through 53 and the load back to 49. If the contacts 40 and 41 are physically connected they will be moved to the right to include more resistance and to the left to include less resistance but if they are separated they can be juggled back and forth to suit particular conditions. It may be desirable to provide a detachable connection between them.

It will be seen that in this construction the portions of the coils 35 and 36 which lie to the left ofthe contacts 54 and 51 respectively form in eifect one resistance, the ends of which are connected to the wires 53 and 56, and that the contacts 54 and 51 are connected to the line by means of the connections 37, 38 and 39. The ends of the coils 35 and 36 are connected to the opposite side of the line from that to which the contacts are connected by means of the wire 52 and the double throw switch 42. Operation of this switch, it is evident, will result in connesting the' ends of the resistance and the contacts to opposite sides of the line selectively. o

From the foregoing it will be clear that the invention results in a rheostat of greatly increased capacity and much wider utility. It can be used in the usual way for the customary purposes and when desired it can be made to handle heavy currents as a resistance unit or to function as a heater.

It will also be clear from Fig. 3 that a plurality of resistance coils canhe connected soas to permit their use either in series or in parallel and such a combination may include ollow cores or any other that may be desired.

The invention greatly enhances the value of the rheostat and not only increases its field as an electrical instrument but makes it p ossible to use it as a heater for a great var1ety of purposes in the laboratory. I am aware that chan es may be made in the form, construction ang arrangement of the invention, as set forth in the selected embodilnent herein, without departing from the scope or sacrificing any of its material advantages, and I consider myself entitled to make all vsuch changes as fairly fall within the scope of the following claims.

I claim:

1. In a rheostat, a plurality of resistance coils, a double throw switch, and wiring between said coils and said switch permitting the resistance to be used in parallel with one throw of the switch and in series with the other throw of the switch.

2. In a rheostat, a resistance, a plurality of slidable contacts connected to one side of a line, the other side of the line being connected to both ends of the resistance.

3. In a rheostat, a resistance, a slidable contact connected to one side of a line, and both ends of the resistance being connected to the other side of the line.

4. In a rheostat, a resistance, of contacts connected with one side of a line, both ends of the resistance being connected to the other side of the line, said resistance being in separate units electrically connected by said contacts.

5. In a rheostat, a resistance, a plurality of contacts connected with one side of a line, both ends of the resistance being connected to the other side of the line, said resistance being in separate units electrically connected by said contacts, and means for operating said units in series or in parallel.

6. A rheostat comprising a hollow core arranged in a horizontal position and adapted to contain a liquid, an inlet for said liquid at one end of said core and at the lower portion thereof, and an outlet for said liquid at the other end of said core and at the upper portion thereof whereby the collection of gases in the top of the core will be prevented.

7. A rheostat comprising a hollow core adapted liquid at the lower portion thereof, and an outlet for said liquid at the upper portion a plurality to contain a l1qnid,an inlet for said.

thereof whereby the collection of gases in the top of the core will bc prevented.

8. A resistance, a conduct or connecting),r the ends of said resistance and havingr a switch therein and a connection between one end of said conductor and one side ot' a line.

9. A resista nee, a. conductor connecting the ends of said resistance and having a switch therein, a connection between one end of said conductor and one side of a line. and means for varyingr said resistance and connected to the other side of the line.

10. A resistance. a conductor connecting the ends oi' said resistance and having a switch therein and a connection between one end of said conductor and one side ota line, a plurality of movable cont-.iets connected to the other side of said line.

11. A plurality of resistance units and movable members making contact with each of said units and connecting them electrically, and means for placing said units in series or in parallel selectively.

12. A vplurality ot' resistance units and movable members making contact with each of said units and connecting them electrically, and means for placing said units in series or in parallel selectively through said contact members.

13. A pair of rhcostats in parallel relation, a member sliding therebetween and contacting with both rheost'ats to connect them electrically, a connection between said member and one side or the other of a line selectively, and means to connect one end of each rheo stat to the other side of the line than that to which said member is connected.

14. A resistance` means connecting the ends of said resistance, means for varying said resistance `and means for connecting said tirst two means to opposite sides of a line.

15. A resistance, means connectingr the ends of said resistance, means tor varying said resistance, means for connecting said First two means to o posi-te sides of a line, and means for reversing said connections.

t PAUL E. KLOPSTEG. 

